This has some grit in it. Give it a good back and forth rub perpendicular to the scratch and finish up with some good circular motions. Put some muscle into this. Wipe this off and check your scratch.

On a recent rainy afternoon, [Thanassis Tsiodras] decided to build his own Forth for the Arduino to relieve the boredom. One week of intense hacking later, he called it done and released his ...